Chemical formula of Histamine: C₅ H₉ N₃

Question 1B

Question 1C

Histamine is soluble in water as it is able to form hydrogen bond with the water molecules. Due to presence of highly electronegative nitrogen atom that are spread all over the molecule, the hydrogen atoms attached to it are highly polarised to be delta positive. As such, the highly electronegative oxygen atoms in the water molecule will be attracted to the hydrogen thus forming hydrogen bond .

There are two parts in the molecule where hydrogen bonding can occur. The first area will be the amine group located at the end of the compound. The other part will be at the 5 membered ring structure where one of the nitrogen has a hydrogen atom attached to it.

Question 2A

Chemical formula for anti-histamine: C₁₆ H₂₁ N₃

Question 2B

The structure shown is commonly named tripelennamine. There are a few similarities in terms of structure between tripelennamine and histamine. Firstly, both structures contain an ‘R’ group (alkyl group or hydrogen) attached to the nitrogen located at the end of the molecule (green circle). Secondly, both structures contain a nitrogen atom in a closed ring(red circle). Both of these components make the structures of histamine and tripelennamine very similar.

Tripelennamine: https://pubchem.ncbi.nlm.nih.gov/compound/tripelennamine#section=2D-Structure

Histamine: http://www.celestialroots.com/histamine.php

Question 3A

Question 4A

Herbal supplements are partially regulated by the authoritites although it is not as intensive and strict as compared to drugs or food. However, even so, manufacturers have to follow a standard procedure when producing or marketing their product.

1. Manufacturers are allowed to claim and market that their product aids in reducing the deficiency of nutrients or even improve certain aspects of health only if they have supporting research and studies regarding it. To do this, they have to acknowledge a disclaimer saying that the authorities have no vet this claim
2. Manufacturers have to ensure that the manufacturing process follows good practice to ensure that all the products produced are consistent and the quality of it meet the minimum standard. This includes having a clean and safe ingredients free from contaminants such as pesticides and bacteria.
3. The relevant authorities have the power to ask the manufacturer to remove the products from the shelves and take legal actions against them once there are reports regarding the safety aspects of the product.

To ensure that as consumers, the issues such as active ingredients, quality control and even side effects, manufacturers are required to do as follows for their product.

1. Write the name of the herbal supplement
2. The full list of ingredients added in the product
3. The recommended serving size, the exact amount as well as the identity of the active ingredient in the supplement
4. The name and address of both the manufacturer and distributor
5. Give warning label stating that consumers should contact the doctor or pharmacist if there are any queries regarding the product.

Question 4B

For Singapore, the Health Science Authority (HSA) has strict control over the herbal supplements that are being sold here. On the HSA website, there is a guideline booklet both for consumers as well as manufacturers regarding the legislation of such supplements. In addition, it is part of the law to ensure that the herbal supplements are safe such as the Medicines Act (Chapter 176), Sales of Drugs Act (Chapter 282) and even The Poisons Act (Chapter 234). This legislation ensures that all rules are strictly adhered to and those that do not confined to this rule will be taken to task.

In addition, the guideline has a complete list regarding the substances that are restricted and prohibited to be added to the supplement. This serves as a guide for the manufacturers who intend to open up and introduce their product in the Singapore market. Information for consumers to validate the safety and quality of the supplement is also part of the guideline booklet. Therefore it serves both the consumers as well as the manufacturer to ensure that everyone is safe.

Text Citation 1:

http://www.hsa.gov.sg/content/dam/HSA/HPRG/Complementary_Health_Products/Overview_Framework_Policies/Health_Supplements/HSGuidelines.pdf 

Text Citation 2:

http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/herbal-supplements/art-20046714?pg=2

Q2a. There is a difference between LDPE and HDPE and that depends on the polymerisation process. LDPE has the most long- and short-chain branching of any form of PE hence it would result in a lower density. The branching prevents it from having a crystalline strucure hence less tensile strength and greater ductility. In summary, LDPE simply does not have the required strength to make the gloves and would most likely break easily when it is being worn.

This is what happens when gloves are made from LDPE. They would simply be too fragile and tear too easily which is why LDPE is simply used for disposable gloves instead of surgical gloves

b. HDPE is produced in the polymerisation process such that the structure resembles more of a crystalline structure. There are lesser branches hence the polymers are lined up in a crystalline manner. Even though the characteristics of HDPE are stronger denser and less rigid, by using a thin liner of HDPE would allow it to have the sufficient level of flexibility.

Q3. When you try and stretch a piece of plastic bag, the strips will tends to narrow. The molecules become aligned parallel to each other and in the direction which you pull the plastic. When the structural dimension of the plastic is being altered, it is not reversible hence it does not go back to its original shape. And when the plastic is continuously being stretched the plastic will eventually break. The key is that the plastic molecules can align to one another whereas in paper, the primary composition is cellulose. Cellulose are far more rigid than plastic hence they are not free to align. They simply tear instead of stretching before breaking.

Q4a. Properties to consider when choosing polymer to use within the human body

1. One of the characteristic is that it should be biodegradable upon the intended time of disposal.
2. It should also be non toxic and non corrosive or does not break down into toxic components that can potentially enter the bloodstream.
3. Capable of maintaining the structural integrity until the intended time of disposal

4. Capable of controlling the rates of biodegradation

b.Contact lens can be differentiated into hard and soft contact lens. Soft contact lens are made from polyacrylamide and it is mostly made of water. Hence it is hydrophilic (water loving) and bonds to the eye. However because it absorbs water, the clarity might not be as good and they are more fragile.

Hard contacts lens are known as RGP which is a mixture of PMMA, fluoropolymers and silicon. By using a mixture of polymers, they are able to enhanced the characteristics such as giving it some flexibility, making it tougher and also they are un reactive to the chemicals on the eye surface. One of the properties desired is that it should be gas permeable which means they allow oxygen to pass through. This allows the eye to stay moist and oxygenated which means it is a much healthier option.

c. Hard contact lenses are made primarily from PMMA whereas RGP is a mixture of PMMA, fluoropolymers and silicons which makes it softer. The harder contacts lens are much more uncomfortable compared to the softer ones and would take a longer time to get used to them. Soft contacts lens can adhere to the shape of the eye hence it is much easier to wear. They also absorb water hence keeping the eye moist. RGP is usually uncomfortable however it has the ability to reshape the cornea hence it might be preferred by certain people.

Q1

a) Coal fired plants produces huge amount of water vapour in combustion process and when this water vapour produced  cooled to form fog reducing the visibility in the area.

b) Average pH of rain –pH 7. Since NPCA reported to be 10 times more acidic than natural, from the pH equation (pH= – log [H+]), the estimated pH of rainfall in the park will be pH6.

Q2

– Hang your laundry to dry it

Hang clothes to dry instead of using the dryer uses leads to less power generation. As such this will reduce amount of gas and coal required to generate the power. Hence lesser contribution to acid rain.

-Walk, bike or take public transportation to work

Cars on the road lead to NO pollutants released which leads to acid rain production. Hence by taking public transport, walk and bike reduces amount of NO production hence reducing acid rain.

-Avoid running dishwashers and washing machines with small loads

This means lesser usage of electrical appliances. As a result lesser power required coming from the gas or coal, hence reduces amount of acid rain production.

-Add additional insulation on hot water heaters and pipes prevents heat from escaping.

Thus, lesser energy consumption to generate heat. Since lesser energy consumption, it reduces fossil fuel consumption thus decreasing acid rain production.

– To buy locally produce and grown food largely reduces the transportation-related acid rain emissions being released into the atmosphere. This is because the transportation used such as trucks , planes and boats are powered by fossil fuels which contributes to sulfur dioxide and nitrogen oxides. These chemicals released leads to acid deposition.

Q3.

a. Acids:

HCl- hydrogen chloride

H2SO4- sulfuric acid

HNO3- Nitric Acid

CH3COOH- Ethanoic Acid

COH(CH2)2(COOH)3- citric Acid

Bases:

KOH- Potassium Hydroxide

NaOH- Sodium Hydroxide

Ca(OH)2- Calcium Hydroxide

Ba(OH)2- Barium Hydroxide

b. Observable properties

-Acids turn litmus paper red while Bases turn litmus paper blue

– All acids taste sour while bases taste bitter.

– Acids tend to be sticky while bases are slippery.

Q4.

Over the years, there is an increasing acidity in the down pour in Singapore. This acid deposition originate from both inside and outside of Singapore’s borders. Singapore having a dense urban development and large industrial base, air emitted from both the industries and motor vehicles releases large amount of pollutants such as Sulphur and Nitrogen oxides which causes acid rain production. This has been an issue to Singapore and strategic ways such as using Near Sulphur-Free Diesel to reduce SO2 emissions diesel industries and vehicles. Alternatively, policies were implemented over the years to curb the amount of pollutants released especially in industrial areas.

Apart from that, smoke haze released from land and forest fires in the region outside of Singapore borders have also affect Singapore’s air quality during the monsoon period.

Question 1

How can you purify your water when you are hiking? Name two or three possibilities. Compare these methods in terms of cost and effectiveness.

There are a few methods to purify water when hiking. Firstly, the most traditional way is to boil water using backpacking stoves. They are usually quite expensive, especially a durable stove. Boiling is effective in eliminating protozoa, bacteria and viruses. However, it will take some time for the water to cool down before you can drink it.

Another method is to use Chlorine Dioxide tablets to purify the water. They are not expensive and convenient for hikers. They are effective in removing bacteria and viruses, but hikers have to wait for 30 minutes to effectively neutralize Giardia and about 4 hours if there is Cryptosporidium is present.

Finally, Ultraviolet purifiers can be used to purify water. These purifiers are rather expensive and require extra batteries when hiking. Furthermore, a filter is required if the water is murky. UV purifiers can also neutralize bacteria, protozoa and viruses.

Are any of these methods similar to those used to purify municipal water supplies? Explain.

Yes, some of the methods are similar. In the case of Singapore water purification system, chlorine is used to kill the bacteria and viruses after the filtration process from the reservoir water. UV rays are utilized to eliminate any viruses or bacteria in the used water in the NEWATER plant.

Question 2

Explain why desalination techniques, despite proven technological effectiveness, are not used more widely to produce potable drinking water.

There are two main reasons on why desalination techniques are not widely used. The first reason is that desalination requires a large amount of energy and it is very costly as compared to other alternative methods. Secondly, desalination has direct impact on the environment. Fish and other marine organisms are killed in the process when desalination plants extract water directly from the ocean.

Hence, given its high operating cost and detrimental effects on the environment, desalination techniques are not favorable in producing potable drinking water.

Question 3

Water quality in a chemical engineering building on campus was continuously monitored because testing indicated water from drinking fountains in the building had dissolved lead levels above those established by NEA.

A) What is the likely major source of the lead in the drinking water?

B) Do the research activities carried out in this chemistry building account for the elevated lead levels found in the drinking water? Explain.

A) The major source of lead in drinking water is due to the corrosion of service pipes and fixtures with lead solder.

B) The lead detected in the drinking water is usually from the corrosion of water fixtures. The effluent from the chemical engineering building does not cause the increase in lead levels as the drainage system is separated from the water supply.

The only possible reason might be that the service pipes are old and worn out, which result in the further corrosion of the lead. Therefore, the research activities do not have direct implication with the lead found in drinking water.

Question 4

Some vitamins are water-soluble, whereas others are fat soluble. Would you expect either or both to be polar compounds. Explain.

Polarity affects some physical properties such as solubility, melting and boiling points. Polarity is used to determine how well molecules can mix with other molecules. Polar compounds can mix with other polar compounds to form a solution but not with a non-polar compound. Also, non-polar compounds mix well with each other but not with polar compounds.

Water molecules are known to be polar and lipid molecules are non-polar. Hence, water-soluble vitamins are actually polar compounds as they can mix well in water. However, fat-soluble vitamins can only mix well in lipids as they are non-polar compounds.

Understanding Earth’s energy balance is essential to understanding the issue of global warming. For example, the solar energy striking Earth’s surface averages 168 watts per square meter(W/m2), but the energy leaving Earth’s surface averages 390 W/m2. Why isn’t Earth cooling rapidly?

Although the amount of energy leaving the Earth’s surface is about double that striking the Earth surface, the Earth does not cool rapidly because the surface absorbs a large amount og energy from the atmosphere due to the greenhouse effect.

Question 2

Decide and explain where the statement (“This winter has lowered my concerns about global warming…”) is correct or incorrect.

Incorrect. Global warming causes adverse climate changes, not just warmer global temperature. Warmer temperatures in one region cause colder winters in another. For example, a hotter, less icy Arctic causes creates a lump of warm air in the lower atmosphere that forces the jet stream to become wavier, dipping south in some places. Thus, the harsh winter as depicted by the thick layer of snow in the comic is a consequence of global warming and should be a concern.

Question 3

One of the first radar devices developed during World War 2 used microwave radiation of a wavelength that triggered the rotation of a water molecules. Why was the design not successful?

The design is not successful because the absorption of microwave radiation by water in the atmosphere interferes with the detection of the intended objects.

Question 4

Now that you have studied air quality (Unit 1), stratospheric ozone depletion (Unit 2), and global warming (Unit 3), which do you believe poses the most serious problem for you in the short run, and which poses the most serious problem in the long run?

I believe that air quality poses the most serious problem in the short run as the effects of bad air quality requires immediate attention. For example, in recent years when PSI levels rise to unhealthy levels in Singapore, people with asthma needed medical attention. Also, school and flights have to be cancelled and delayed. Thus, due to the adverse immediate effects, this is the most serious problem in the short run for me.

In the long run, the most serious problem is global warming. Since the adverse effects of global warming like rising sea levels and extreme climate change are delayed, there is a lack of awareness and sense of urgency in people. This causes people to only take action to curb this problem after the dire consequence are too late to be salvaged. This will inevitably cause the effects to multiply in the long run, leading to catastrophic effects.

a. A charcoal briquette burns.
Exothermic. The Carbon molecules loses chemical potential energy as heat during combustion.

b. Water evaporates from your skin.
Endothermic. Liquid water molecules gain energy from the surrounding to change from a liquid to gaseous state.

c. Ice Melts.
Endothermic. Solid water molecules gain energy from the surrounding to change from a solid to liquid state.

Question 2: Chemical explosions are very exothermic reactions. Describe the relative bond strengths in the reactants and products that would make for a good explosion.

The bond strengths of the reactants are usually very strong as they require a high amount of energy to break apart the atoms. The bond energies on the other hand, are much larger in the products than that of the reactants. This will result in a large net negative energy change which indicates a large exothermic reaction (aka explosions).

Question 3: How might you explain the difference between temperature and heat to a friend? Use some practical, everyday examples?

Heat is defined as the energy that flows from a hotter to a colder object.
Temperature determines the direction of a heat flow. Heat always flows from a hotter region to a colder region.

Taking the simple process of adding ice cubes to a hot cup of coffee.
Beforehand, we are aware that if you touch the ice cube and hot coffee, you will feel a cold and hot sensation on your skin directly. This is the temperature of the objects which determines which is hotter than the other.

When ice cubes are added to the coffee, the ice melts, dissipating cold water around that mixes with the coffee. This energy that is transferred from the hot coffee to melt the ice cubes is know as heat.

Question 4: A premium gasoline is available at most stations has an octane rating of 98. What does that tell you about:

a. the knocking of this gasoline?
Octane rating is a measure of the ability of gasoline to burn smoothly without knocking. An octane rating of 98 means that the gasoline has a knocking characteristic of a mixture comprising of 98% isooctane and 2% heptane. This means that it is generally resistant to knocking

b. whether the fuel oxygenates?
In general, additives which are added to fuels determines the degree of oxygenation. Moreover, such additives tends to give the fuel a higher octane rating. However in this situation, we are unable whether the fuel oxygenates simply based off the octane rating of 98.

Ozone screen or ozone layer?

Never had I given much thought to the terminology of these things. Through this exercise, I realised the features of this ozone concentrated zone in the stratosphere.

Also, the problem of the ozone hole is often simplified and misunderstood as one that can be solved by sending large amounts of ozone into the stratosphere. However, this may be do more harm than intended. Like what was mentioned in the lecture, this will cause the equilibrium to shift, causing even more ozone to be depleted.

In spite of the various policies in place to ban products that depletes the ozone, the damage done across the years are too severe to fix already and the policies implemented are just to reduce the rate at which the ozone is depleting. Hopefully in time to come, our actions towards saving the earth and its ozone will be successful.